In tropical settings, the diagnosis of infectious etiologies of fever remains challenging, owing to the complex epidemiology of parasitic, viral, fungal, and bacterial causes and the suboptimal performance of current diagnostics. Multiplex molecular pathogen detection systems are now routinely used in the developed world to interrogate respiratory and blood specimens, and there remains an ongoing need for simple, rapid, multiplex, and sensitive platforms for point-of-care diagnostics for tropical pathogens. In this project, a novel nanophotonic, PCR-free, incubation- independent, sequence-based detection platform for bloodborne tropical pathogens that cause fever will be developed and field-tested. Specifically, in the initial R21 phase, a multiplex nanophotonic chip based upon plasmonic `nano-rattles' will be designed and engineered that can detect unamplified nucleic acid targets in two species of malaria parasites, dengue and chikungunya viruses, spotted fever group Rickettsia, and Leptospira interrogans, and its operating characteristics will be quantified by comparison with reference diagnostics using banked field samples from Kenya, Cambodia, and Sri Lanka. Upon achievement of transition milestones based upon these operating characteristics, in the R33 phase, the assay will be further developed by 1) engineering and building an integrated testing unit suitable for field use, and 2) deploying the assay for pathogen detection in prospective cohorts of febrile patients at field sites in western Kenya and western Thailand. The overall goal of this project is to produce a field-ready diagnostic system which sensitively and simultaneously detects 6 major bloodborne tropical pathogens in unprocessed whole blood specimens. To achieve this, this proposal is submitted by co-PIs with expertise in nanoplasmonics, bioassay development, optical sensing, tropical medicine, and epidemiology, and partners with collaborators in molecular diagnostics and tropical clinical research. This interdisciplinary team of investigators is committed to improving molecular diagnostics for tropical pathogens in order to improve the clinical care of patients with fever in the tropics and enhance the ability to track and detect emerging tropical diseases.